1. Field of the Invention
This invention relates to a fuel injection pumping apparatus for supplying fuel to a compression ignition engine and of the kind comprising a cam actuated pumping plunger housed within a bore, means for supplying fuel to the bore, an outlet from the bore and through which fuel can flow to an associated engine and a spill valve operable to allow fuel to spill from the bore thereby to control the quantity of fuel supplied through said outlet, said spill valve including a valve member coupled to a piston which is slidable within a cylinder, resilient means acting on the piston to bias the valve member into engagement with a seating defined about a spill passage which opens into an end of the cylinder and valve means operable to supply fluid under pressure to said one end of the cylinder to lift the valve member from the seating.
2. Description of the Prior Art
An example of such an apparatus is seen in GB-A-2253445. In such an apparatus neglecting leakage, all the fuel which is spilled from the bore flows into the one end of the cylinder to displace the piston against the action of the resilient means. The spilled fuel is returned to the bore which is then supplied with further fuel from a source to displace the plunger outwardly its maximum extent.
The bore is formed in a distributor member part of which is rotatably mounted in a body part of the apparatus, there being a very close working clearance therebetween. The aforesaid outlet is in the form of a passage which extends within said part of the distributor member and in the operation of the apparatus the fuel becomes heated and heat is transmitted to the distributor member which as a result expands and causes a reduction in the working clearance. This reduction in the working clearance leads to the possibility of seizure and there is a particular risk at high speeds due to the increased fuel pressure.